Sclerocactus cloverae (Clover's cactus)

Sclerocactus cloverae (Clover's cactus)

Photograph by Daniela Roth (2020)
Family
CACTACEAE
Scientific Name with Author

Sclerocactus cloverae K.D. Heil & J.M. Porter

Synonyms

Sclerocactus cloverae ssp. brackii K.D. Heil & J.M. Porter; Sclerocactus cloverae ssp. cloverae K.D. Heil & J.M. Porter; Sclerocactus coveriae ssp. cloveriae K.D. Heil & J.M. Porter; Sclerocactus cloveriae ssp. brackii K.D. Heil & J.M. Porter; Sclerocactus cloveriae K.D. Heil & J.M. Porter; Sclerocactus whipplei (Engelmann & J. M. Bigelow) Britton & Rose var. heilii Castetter, P. Pierce & K. H. Schwerin; Sclerocactus whipplei var. reevesii Castetter, P. Pierce & K.H. Schwerin; Pediocactus cloverae (K. D. Heil & J. M. Porter) Halda

Common Name
Clover's cactus; Clover's fishhook cactus
Rare Plant Conservation Scorecard Summary
Overall Conservation Status Documented Threats Actions Needed
UNDER CONSERVED

Oil & gas development, insect and rabbit herbivory, wood cutting, grazing impacts, OHV traffic.

Population trend monitoring, threat impact monitoring (dust, transplanting, rodents & rabbits, drought, oil & gas development), seed banking.


Description

Stems unbranched (occasionally 2-3-branched near base), green, ovoid to elongate-cylindric, 2.9-25(-35) × 2.8-12.5(-20) cm; ribs usually (11-)13(-15), well developed, tubercles evident on ribs. Spines obscuring stems; radial spines 4-6 per areole, acicular, elliptic or rhombic in cross section, 19 × 1.3-2 mm; central spines 6-9 per areole, usually 8; abaxial central spine usually 1 per areole, porrect, straw colored to brown, highlighted with purple or red, terete or somewhat angled, hooked, (15-)30-46 × 1.5 mm; lateral central spines 5-8 per areole, similar to abaxial but slightly shorter and usually not hooked; adaxial central erect, white or straw colored, straight or curved, angled to flat, somewhat inconspicuous, triangular in cross section, 25-55 × 1-2 mm. Flowers narrowly funnelform to campanulate, 2.5-3.5(-4) × 1.6-3.1(-3.6) cm; outer tepals with greenish to purple with brownish midstripes, pink, purple, or whitish margins, larger ones oblanceolate, 10-18 × 4-7.5 mm, margins membranous and crisped or minutely toothed, apex mucronate; inner tepals purple, sometimes suffused with brown, largest tepals oblanceolate, 15-22(-30) × 4-6 mm, margins irregularly toothed, apex mucronate; filaments white, tinged with pink to pink-purple; anthers yellow; ovary minutely papillate, appearing smooth. Fruits irregularly dehiscent or dehiscent through basal abscission pore, green to tan, sometimes suffused with pink, 7-15 × 5-12 mm, dry; scales few, membranous, scarious-margined, minutely toothed or fringed. Seeds brown or black, 1.2-2.5 × 1.9-3.5 mm; testa with rounded papillae. (Flora of North America, Vol. 4, 2003).

Flowering late April to early June

Similar Species

Sclerocactus cloverae is similar in appearance to Sclerocactus parviflorus but has more dense spines and smaller purple flowers. S. cloverae flowers: 2.5-3.5(-4) × 1.6-3.1(-3.6) cm; radial spines: 4- 6 per areole; S. parviflorus: flowers:(2-)3-5.7(-7) × 2.5-5.5(-8) cm; radial spines: 8 - 17 per areole

Distribution

New Mexico: San Juan, Sandoval, and Rio Arriba counties. Colorado:  La Plata County

Habitat

Sandy clay strata of the Nacimiento Formation in sparse shadscale scrub; sandy, gravelly, or clay hills, mesas, and washes, desert grasslands, saltbush, sagebrush, and rabbitbrush flats, pinyon-juniper woodlands; 1,500 - 2,200 m (4,921 - 7,217 ft).

Remarks

A genetic analysis in 2018 found that subspecies brackii was not genetically distinct from subspecies cloverae (Porter & Clifford 2018).  Hence the two subspecies were combined into S. cloverae.

The same analysis found that Clover’s cactus (both former subspecies combined) displays a high degree of genetic differentiation across its range and populations in the southern portion of its range should be considered a distinct genetic element.

Conservation Considerations

Oil and gas development is the most significant current and active threat to most populations of the species, and especially to the largest population, which occurs in the vicinity of Lybrook (Muldavin et al. 2016).  The majority of known occupied sites and habitat occurs within areas of active oil and gas leases on BLM lands (80%).  Additional threats include insect and rodent/rabbit herbivory, OHV traffic, grazing impacts, wood cutting, and climate change.

Important Literature

*Heil, K.D. and J.M. Porter. 1994. Sclerocactus (Cactaceae) a revision. Haseltonia 2:20-46.

Flora of North America Editorial Committee. 2003. Flora of North America, Volume 4. Oxford University Press, New York.

Muldavin, E., R. Sivinski, M. East, Y. Chauvin, and Mark Horner. 2016. Brack's hardwall cactus distribution, habitat, aMuldavinnd status survey 2015. Unpublished report prepared for the BLM State Office, Santa Fe, NM by Natural Heritage New Mexico, Museum of Southwestern Biology and Department of Biology, University of New Mexico, Albuquerque, NM. 61 pp. [https://nhnm.unm.edu/sites/default/files/nonsensitive/publications//NHNM_BracksCactus2015SurveyReport_Final20160506.pdf]

Porter, M.J. and A. Clifford. 2018. Genetic diversity within Sclerocactus cloverae Heil & Porter based on ddRAD-seq: the genetic basis for subspecies recognition. Final report to the BLM New Mexico State Office, Santa Fe, NM.

Information Compiled By
Daniela Roth 2020

For distribution maps and more information, visit Natural Heritage New Mexico